Project Summary/Abstract The brain is by far the most complex and heterogeneous organ in the human body. For years, there has been a growing and unmet need to develop multielectrode arrays for neurotransmitter sensing in multiple brain regions simultaneously. Disparate brain regions such as the nucleus accumbens, striatum, prefrontal cortex, hippocampus, and others have been widely known to have greatly varying electrical and neurochemical properties from one another. Until recently, we have been limited by technological capabilities in achieving this goal. With the development of novel electronics such as the multichannel potentiostats by Pine Research, multielectrode arrays now have the capability of being interfaced with these potentiostats to perform neurochemical sensing. Microprobes for Life Science (MLS) has been a leader in the development of multielectrode arrays for several years with a national and international customer base. MLS has developed this research collaboration with Alexander Zestos, a bioanalytical electrochemist and neuroscientist. Dr. Zestos has expertise in the development of novel electrode materials for neurotransmitter detection with fast scan cyclic voltammetry (FSCV). FSCV is an important technique that allows for the detection of neurotransmitters at sub-nanomolar limits of detection and sub-second temporal resolutions. At this moment, this multielectrode arrays for neurotransmitter detection are currently not available commercially, yet are very high in demand. Dr. Zestos and MLS will develop the multielectrode arrays through two independent approaches. Aim 1: Carbon fibers will be coated in parylene in a deposition chamber and used to make multielectrode arrays. Aim 2: Tungsten and Platinum-Iridium microelectrodes will also be deposited and insulated in parylene, and then coated in carbon to make multielectrode arrays. Approaches of depositing carbon onto the metal microelectrodes include dipcoating in suspensions of CNTs dispersed in solvent or the deposition of vertically aligned graphene through plasma enhanced chemical vapor deposition (PECVD).